Unloader



B. S. AIKMAN May 8, 192s.

UNLOADER 2 Sheets-Sheet 2 Filed July 7. 1927 Patented May 8, 71928.

UNITED STATES PATENT OFFICE.

BURTON S. .AIKMAN, OF MILWAKEE. WISCONSIN, ASSIGNOR TO NATIONAL BRAKE & ELECTRIC COMPANY, OF MILWAUKEE, WISCONSIN, A` CORPORATION OI'WIS- CONSIN.

UNLOADER.

Appucauon mea .my 7, 1927. serial No. 203,92a

My invention relates to unloaders for compressors.

In certain forms of compressors recently developed by me, the intake valve comprises a sleeve actuated by the friction of the piston or the piston rings thereupon. Preferably, this sleeve seats against the bottom of the cylinder head during the compression stroke to provide a closed working cylinder, and the sleeve is moved away from its seat by the ring friction when the piston starts reverse motion.

In the smaller sizes, and'particularly for intermittently operating` compressors, it is generally unnecessary to provide any unloading means, since the valve will open with reverse motion of the piston, to permit the escape of any air compressed in thek cylinder, or to permit escape of any compressed air leaking back into the cylinder past the discharge check valve. Upon starting of the motor, all that isrequired is normal compression from atmospheric pressure to the terminal pressure, and that `can generally be performed by the motor, even though the same may be temporarily overloaded.

On the larger sizes, or on higher compression ratios, the heavy rush of current caused by starting under load is so objectionable that an unloader is desirable. Also. on continuously driven compressors it is desirable to provide unloading means which will unload the compressor after the pressure in the receiver has attained a predetermined value.

It is the aim of the present invention to provide an unloader of simple, reliable and inexpensive construction which will act to unload a compressor of the above described type.

In order to acquaint those skilled in the art with the manner of constructing and op- @rating a device embodying my invention, I`

a compressor embodying an unloader ot` my invention; y

Fig. 2 is a horizontal cross-sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a vertical longitudinal section similar to Fig. l, showing a modication of my invention; y

Fi 4 is a horizontal sectional view of a modi cation of the invention in which the unloader isarranged to unload a two-cylin-` der compressor ot this type; and

Fig. 5 is a diagram of connections for purposes of explaining the mode of operation oi. the invention.

Referring now to Fig. 1, the compressor 1 is normally driven by an electric motor which is stopped and started under the control of a switch, which may be either manually'or automatically operated.l and which is not shown for the sake of clearness. The compressor 1 discharges by way of a discharge line 2 to a reservoir 3. A pressure regulator 4 connected to the reservoir 3, operates on the attainment of a predetermined maximum pressure in the tank 3 to close the atmospheric vent 5 to the unloader cylinder 6 and to open the pressure connection 7 to said unloader to stop further compression of air or other gas until such time as the pressure in the reservoir 3 drops below a predetermined minimum, whereupon the regulator 4 shuts off the connection of live air to the regulator 6 and opens the atmospheric vent 5 to said regulator 6 to cause the same to act to permit the compressor to function.

Referring now to Fig. 1, the cylinder 8 has a suitable flange 9 at its upper end from which rise the posts or webs 10. To these posts or webs 1 0 the head member 11. is bolted. At its upper end the cylinder 8 has an inwardly extending ange 12 forming a guide for the upper end of the ,valve sleeve 13. At its upper end the valve sleeve 13 has. exter nally, a conical shoulder 14 terminating in an annular rim which is faced off normal to the axis ot the sleeve 13.

The head 11 has a thin annular disc 16 clamped under the inner edge of a clamping ring 17. rlhe inner edge of the ring 16 is free and overhangs a shallow groove 18 formed in the bottom of the cylinder head 11 to permit the interior of the sleeve 13 to connnunicate with the space back of said ring 16 when the sleeve is raised into contact with the ring 16.

The cylinder head 11 has a. discharge passageway 19, preferably of conical shape, extending up through an integral neck 20.

charge valveA pocket. The upper endofthis'4 chamber 1s closed by a. fitting 24, Whiclrhas a spring guide Q5 depending into the pocket 23 and 'forming a stop for upward motionxrf the valve 21. A suitable colnpresslon spring 26 applies thevalvefl, to its seat., The file-Y ting 24 has a. pipe socket 27 to-connectthe dischargev pipe 2 forleadinggaway the-hot compressed air..

The valve sleeve 13-ahas a collar QSIorm-r ing at its upper side ashoulden adaptedto be engagediby the limbs et a` forked lever 30. Thislever forms.theunloading lever forthe valve sleeve 13. It is hinged? for,- a short swingingmotion onzthe'pinf 31, which eX- tends. through' they lugs, l2-.32, preferably. cast integralwiththe flange 9. A smallfcoinpressionspring, 33 is seated in.` a, pocket 341 helonv the .main stem ofv the leven.. and this springt tendsat all timesto raisethevlimbs of the forked, lever 30 out, of1 contactwith the-shoulderformed by; the upper sur-face'o'f the collan 28.

TheA collar S-provides-:u shoulden at its lower face adapted toengage-the nesilient stop 35Which restrains the downwardmd tion of the sleeve\13.

The valve sleeve 13 contains at Work-ing syst-cm; 36 providedV with a suitahledome or projection 3,7 adapted toenter-the discharge port 19 fon the sake of minimizingv thefoleari ance space. Thepistonf 36fis provided with oneonmore metal packing rings 3870i the split` ring ty.pe,or any pnefenred type, for securing a tight fit hetnveen` saidl piston and the inner,- walL of thesleeve' 13. 'Ehe-sleeve 1-3- is act-uatedybv. the movement of thepiston 36.,being dragged up or dow-nr, asy the case may-be, by theirictionof the piston 36 4with the interior surfactant-theslee-ve'13; In detail` itl is thev friction oit-the.- spliti rings- 38 enpanded; into contanti with.. the Wallsof; the sleeve 13 which` permits.thepistoin to-seize thesleevesulicientlv to-cause it toboimoved upy ordownat. the beginningof. an up or down stroke of the piston. Thesleeve 13 is` guidedz in al suitable guide at. its lower end-noth-` shown.k Y

The 'head member 11 has. athreadedsOckGt 4() Whi ch is adapted. to receive f the A threaded stud 4.15 formedfoir the lower` endio the un loadingeylinden 412. rEhis. unloading eylinf der 42 has. aremovable head 43 .threaded on its. upper end. andprovidin a pipo-socketA 44 for the connecting pipe 7 'from4 the reguf later 4.., A- suitablepistonldsfitted in the cylinden42 and itf has asteml 16 l which ex.- tends. down. through a holeV in; the. Harige'4 of the head member 11 Where it may engage at its'lower end the pivoted unloading lever 30 for forcing the valve sleeve 13 downwardly against its resilient stop 35.

A spring 47 tends normally to raise the piston 45 and stem 46 out of contact with the lever30.

Due to the ample cooling which is'secured inacmnpressor of this type, it is possible to mount the unloading cylinder 112 directly uponthecylinder head. The return of heat from the discharge valve chamber 23 to the eylinderhead llvis preventedby. the neekfQO of reduced cross-section of metal oilow. hea-t conductivity. f

The operation ofthe dev-ice is asr follows f Assumingthat the piston, 36. is. risingrV on the compression, stroke, the friet-ion oi. the rings 38 with the interior of the sleeve 1:3 raisestheupper'end.sunface 15 or' ysaid-sleeve iiitocontact with the inargingo. the flexible metal ringldclosing the cylinder for comy pression. While the member 8 isterined. a cylinder. the actual Working VcylinderA is de,- fined-by theslecve 13and thefhead 1.1 and piston 36.. As-the piston.lreachesithe up1- per endoi"` itsstrolre and l'lasrdiseharged. the contentsoff the. working cylinder past, valve 2l. it; comes `for abrief, periodo. time to rest and reverses its. direction. As. itreverses, theffriction of the rings.38 onthe inside of the sleeve 13 pull, the. cylinder downuntil the collary 28Y engages the stop. 35..` further motiondraw-infr in air over the topY edge 15 of the sleeve. into the Working cylinder.. When thereceiver 3 has beencharged tothe predetermined pressure, thev controller 4:

closes oft'l the atmospheric vent iand admits pressure. fromthe. receiver 3,to the pipe 7.

The compressed. air, acting. upon the piston 45forcesthe rod 46idown intocontact with the leverA 30 Withsufficient force to overcome the-pressureofthe spring 33.,and either to forcethesleeve valve downwardly at once, or to do soupon thenext suctions rokezand thereafter-to hold itopen to prevent further compression of gas. 1t is not necessary. that the nnloader be made powerful enough. to pnslr thesleeve 13 dmvmvardly duringv a compression strokeit need only be of sufli+ cientponen toholdqthe sleeveY 13open against the'tendency of the ring friction to close the same.

lathe structure shownin Fign, the-conn pressor structure is substantially the same as showningFig. 1. In-this case, howeverthe lngy .'Ovreplaces the lugs 32 and it -for-insa guide for the unloader plunger 51, which has a tapered end, as shown at 52, adaptedto ridelupon the-conieal'or` tapered surfacel ol the sleeve valve 13. Inthis. case, theuln loader mot-or comprises a motor framef having a-suitablecircular flange 51 to which there is clalnpedby means of thecompanion lang fe55onthemotorr chamber 56. a flexible diaphragm 57 bearing against the inovable piston member 58 having the stem 51 secured thereto. The motor fram-e 53 is connected by a clamping flange or foot 59 to the integral lug forming a part of the cylinder trame 8. A compression spring seating in a pocket in the bottom of the frame 53 urges the piston 58 and the plunger 51 to the left so that the tapered end 52 lies out of the way of the movable valve sleeve 13. The part of the plunger 51 which extends into the lug 50 is formed preferably of: square cross section so as to maintain the proper position of the tapered face thereof.

rIlhe operation of this embodiment is as follows When the controller 4 operates to close the atmospheric vent 5 and admits pressure to the pipe 7 leading to the unloader 6, the diaphragm 57 is forced to the right carrying the piston 58 and plunger 51 with it and forcing the tapered face of the plunger 51 into engagement with the `conical shoulder 14 on the valve sleeve 13. This pressure may be made great enough to force the sleeve 13 downwardly during the compression stroke, or it may be, in the case of a single cylinder, only great enough to block the upward rise of the sleeve after the sleeve has descended on a suction stroke, the wedging face 52 being thus in place to prevent rise of the sleeve thereafter.

In Fig. 4 I have shown the manner in which a compressor of the two cylinder type embodying the sleeve valve may be unloaded by an unloader of m invention. case, the plunger' 51 has a tapered face at its lower :trent edge adapted to engage simultaneously the shoulders 14-14 of the two cylinders 13-13.

The plunger 51 is preferably of nonseircular cross-section, for example being square, and connected by a round portion 62 to the piston 63 playing in the unloader cylinder 64. The plunger 51 is normally held out of the way ot' the valve sleeve 13-13 by a suitable spring 65. When the regulator 4 closes olf the atmospheric vent 5 and admits live pressure to the pipe 7, the plunger 63 is thrust` downwardly, as viewed in Fig. 4.

In this construction, the pressure of the piston 63 is preferably suiliciently powerful to force both of the sleeves 13 downwardly, but by allowing a small rocking motion of the plunger 51', the sleeves may be held open, one at a time, as they are opened by ring friction. That is to say, assume that the right hand sleeve 13 first moves downv when the piston 51 is thrust downwardly as viewed in Fig. 4. Rocking of the plunger 51 permits it to hold the right hand sleeve 13 down, and then when the le'l't hand sleeve 13 is moved downwardly by ring friction the plunger 51 advances further and rocks at the same time to catch the sleeve 13 in open position. Thereby both Sleeves are In this actuated by ring friction, 'it is to be understood that it might be actuated by cam motion through a suit-able yieldable connection as through a compressionspring of a given strength and blocking of the sleeve valves in the open position would result only in compression of such spring connection. My invention is applicable to sleeve valves f where the operation of the same is through a yieldable mechanism.

The lever 30 of Fig. 1 may be employed for unloading two cylinders as well. In that case, a lateral rocking motion is permitted for holding down first one valve sleeve while the other is raised, and then holding down both upon the opening of the second.

1. In a compressor, a cylinder, a head, a sleeve valve having a seat upon the head, an unloader cylinder having a piston, and means actuated by said piston for holdingr said sleeve away from its seat on said head to unload the compressor.

2.'In a compressor, a cylinder frame, a valve sleeve therein, means cooperating with the valve sleeve to form a closed working cylinder, a piston in the sleeve, said sleeve being moved by the friction of t-he piston therein to open and close the valve sleeve, and means for blocking the valve sleeve in open position ttor unloading the compressor.

v3. In a compressor, a cylinder, a head, a sleeve valve having a seat upon said head, said sleeve having a shoulder and an unloader member adapted to engage said shouldei-to hold said sleeve away from said head to unload the compressor.`

4. In a compressor, a cylinder, a head, a sleeve 'valve having a seat upon said head, an unloader cylinder having a piston, said sleeve valve having a shoulder and a member controlled by said piston adapted to engage said shoulder to hold said sleeve away from said head to unload the compressor.

5. In a compressor, a cylinder, a head, a sleeve valve having' a seat upon said head, an unloader cylinder having a piston, said sleeve valve having a shoulder, and a member adapted to travel in a plane normal to the axis ot said sleeve valve for engaging said shoulder to hold the sleeve valve open to unload the compressor.

6. In a compressor, a cylinder, a head, af sleeve valve having a seat upon said head, an unloader cylinder having a piston, said sleeve'xv-alve havingian inclined Sliouldelrn'nd a wedge member aotuatedby said piston and adapted toitravel along-saidslioulden to. hold vtlm'slelnwevalve oil" of its sent for unload@ ing the oompresson.

7 In; :n cmnpressor,. af cylinder frame, :L wllveslemfc; theiei11;.11ioa11s cooperating with the. valve sleeve to form aclosed Working cylinder.'7 a pist-omini the sleeve, said sleeve being, moveflby the` friction of thel piston 10 

